Controlled brightness luminous panel luminaire



N '17, 1959 w. L; LIPSCOMB 2,913,515

CONTROLLED BRIGHTNESS LUMINOUS PANEL LUMINAIRE Filed June 27, 1955 26/, INVENTOR.

WILLIS L. LIPSCOMB I 1,913,575 CONTROLLED BRIGHTNES'S LUMINOUS .PANELLUMINAIRE Willis L. Lipscomb, San Diego, i I Application June 27, 1955, Serial No. 518,168 iClaims. (CL 240 41.11) I The present invention relates generally to luminaires and more particularly to a controlled brightness luminous panel luminaire.

The primary object of this invention is to provide a luminaire having a translucent diffuser panel designed for reducing unwanted brightness or glare.

An ancillary object of this invention is to provide a light diffusing and distributing shroud element which can be classified generally with light diffusing panels and bowls commonly used. in luminaires but which prevents undue brightness contrast between .the adjacent ceiling and the luminaire, with a transmission factor increasing as the distance from the ceiling increases since this is easily tolerated, and the area of maximum brightness is hidden from view from the side of the luminaire. This nite States Pate object is accomplished by providinga reentrant portion and varying the light transmission capacity of the diffuser element progressively from minimum adjacent the ceiling to maximum at the re-entrant portion. 1

Another object of this, invention is to provide a luminaire having a diffuser panel which is easily attached and removed and which is self-retaining without the use-of screws or other fastenings. t

Anothcrobject of this invention is to provide a luminairein which the diffuser panel isterminally enclosed by end plates havingb'affles thereon to prevent light leakage, the baffles having flexible portions to facilitate removal of the diffuser. g

Another object of this-invention is to provide a lumina-ire which is suitable for attachment to a ceiling surface or for a semi-recessedinstallation.

Another object of this invention is to provide a 111-.

Finally, it is an object to'provide a lurninaireof the aforementioned character which, is simple and convenient to install and service and which will give generally efiicient and durable service.

With these and other objects definitely in View, this invention consists in the novel construction, combination and arrangement of elements and portions, as will be hereinafter fully described in the specification, particularly pointed out in the claims, and illustrated in the drawing which forms a material part of this disclosure.

Fig. 1 is a perspective view, from below, of the luminaire as mounted on a ceiling surface.

Fig. 2 is a vertical transverse sectional view thereof.

Fig. 3 is a fragmentary sectional view taken on the line 3-3 of Fig. 2.

Fig. 4 is a sectional View similar to Fig. 3 but showing the luminaire mounted as a semi-recessed fixture.

Similar characters of reference indicate similar or identical elements and portions throughout the specification and throughout the views of the drawing.

Referring now to Figs. 1-3 of the drawing, the luminaire comprises an elongated inverted housing 10 having downwardly sloping side panels 12 and end panels 14, the lower edges of said side panels being folded inwardly 2,913,575 Patented Nov. 17, 1959 26, of plastic or the like, which is generally W-shaped in cross section. The shroud or diffuser 26 has downwardly extending side panels 28 which slope inwardly and are slightly convex on their outer surfaces and more nearly planar on their inner surfaces with the greatest thickness of the panels at the upper edges and the thickness progressively decreasing toward their lower edges. The lower ends of the side panels 28 are interconnected by a central re-entrant portion 30, which comprises a pair of upwardly and inwardly sloping re-entrant panels 32 having convex outer surfaces. The upper edges of the side'panels 28 have outwardly projecting longitudinal flanges 34 formed integrally therewith, which flanges fit into the support channels 16 of the housing 10.

Since the shroud or diffuser 26, is translucent rather than transparent, this progressive'thinning, toward the lower edges effects a progressively varying light transmission capacity increasing toa maximum at the juncture of the panels 28 with the panels 32 of the re-entrant portion 30', and the. panels 32 are of a thickness preferably approximately equal to the minimum thickness of the panels 28 so that the light transmission factor of the re-entrant portion 38 is very high.

The ends of the diffuser 26 are enclosed by endpanels 36 of flat sheet material shaped to fit the outer crosssectional contour of said diffuser, the end panels and diffuser preferably-being of the same material, although this isnot essential and the end panels maybe metallic, if desired. .Each end panel 36 has abaffle strip 38 fixed to-the inner face thereof, said strip being slightly spaced from ,and parallel to the outer edgeof the panel, and

surface of a ceiling, as indicated at 41 in Fig. 2 and may be used singly or in multiple. In the multiple installation the 'luminaires are merely mounted end-to-end with end panels 36 used on the end diffusers only, the abutted diffusers 26 being joined by suitable interconnecting strips if necessary. i I

The specially shaped diffuser 26 has a large overall surface area and provides a very satisfactory downward light component. However, the re-entrant portion 30, While contributing to downward light transmission, is not visible or only partially visible from the sides of the fixture and this reduces the apparent rightness from the sides. Even .when the luminaire is ceiling mounted above the normal line of vision, the diffuser is more likely to be viewed from the side than from below, and the reduced visible area greatly reduces eyestrain. Thus by using a re-entrant portion in the difiuser, a maximum of actual light transmission surface is obtained with a minimum of normally visible surface. The baifie strips 38 effectively prevent light leakage between the endpanels 36 and the diffuser 26. This shroud or diffuser therefore, prevents undue brightness contrast between the .adjacent ceiling and the luminaire, with a transmission factor increasing as the distance from the ceiling increases, since this is easily tolerated, and the area of maximum brightness is hidden from view from the side of the luminaire. It is important to note that the density of the panels 28 may be varied in the same manner as the thickness thereof to achieve a desired variation in light transmission capacity. It is also noteworthy that since the material is flexible, the greatest flexing will occur adjacent the area of least thickness, that is, at the juncture of the panels 28 with the panels 32, as will now be explained.

Removal of the diffuser 26 for cleaning or lamp servicing is extremely simple. The material from which the diffuser is made is substantially resilient and the diffuser is easily compressed at its upper edges to release the flanges 34 from the support channels 16 as shown in dash line in Fig. 2, so that it can be removed. The free ends 40 of the baflie strips 38 bend inwardly and allow the diffuser 26 to be compressed. Replacement is accomplished by compressing the diffuser and allowing the flanges 34 to snap back into place in the support channels 16. It will now be evident that the reduction in thickness of the panels 28, toward their lower edges has two functions, namely increased light transmission and localization of the actual flexing to portions of the panels 28 as distant as possible to the upper edges of the panels 28 to avoid any tendency toward sagging or warping, it being understood that the flexing is considerably restricted at. the ends of the panels by the inwardly extending flanges 39.

The luminaire is also suitable for semi-recessed installation with a slight modification of supporting structure as shown in Fig. 4. The ballast box 18 is suspended from strap hangers 42 which are secured to joists 44 above the ceiling 46, said box projecting downwardly through an opening 48 cut in the ceiling. Extending outwardly from the ballast box 18 are support channels 52 at their outer edges, said plates being mounted against the surface of the ceiling 46. The lamps 22 are held in conventional'socket members 54 suspended from the ballast box 18. The diffuser 26 is held with its flanges 34 in the support channels 52, the method of attaching and removing the diffuser being as previously described.

The operation of this invention will be clearly comprehended'from a consideration of the foregoing description of the mechanical details thereof, taken in connection with the drawing and the above recited objects. It will be obvious that all said objects are amply achieved by this invention.

Further description would appear to be unnecessary.

It is understood that minor variation from the forms of the invention disclosed herein may be made without departure from the spirit and scope of the invention, and the specification and drawing are to be considered as merely illustrative rather than limiting.

Iclaim:

1'. A luminaire comprising: an elongated frame including a lamp supporting element having means for operatlvely mounting lamps thereon; said element having longitudinally extending lateral portions; an elongated diffuser of light conducting sheet material and having upwardly divergent side panels; the upper longitudinal edges of said side panels having means engageable with said lateral portions whereby the diffuser is suspended from said portions; said diffuser being resilient and said means being disengageable from said lateral portions by manual deformation of the diffuser to permit removal of the diffuser; end panels of flat sheet material secured to said frame; said end panels having baffle strips integral with and projecting longitudinally of the luminaire from the confronting faces of the end panels and fitting closely within the ends of said diffuser; said baflle strips having lower portions extending across the entire lower end portions of the diffuser and constituting means to block at their lower ends with reference to said end panels and comprising free upper ends adjacent the upper portions of said side panels to block light from escaping between upper portions of the end panels and the diffuser, while also permitting inward displacement of the side panels when said means are disengaged from said lateral portions.

2. A luminaire comprising: an elongated housing having lamps operatively mounted therein; the longitudinal edges of said housing having inwardly turned support channels formed thereon; a diffuser of light conducting, resilient sheet material removably attached to said housing; said diffuser being substantially W-shaped in cross section and having downwardly and inwardly sloping side panels, slightly outwardly convex; a re-entrant portion interconnecting said side panels at the lower edges; said re-entrant portion having upwardly and inwardly sloping opposed panels, slightly outwardly convex; the upper edges of said side panels having outwardly'turned flanges thereon engageable in said support channels; end panels of flat sheet material shaped to fit the cross sectional contour of said diffuser; said end panels having baffle strips integral with and projecting longitudinally of the luminaire from the confronting faces of the end panels and shaped to fit closely within the ends of said diffuser; said baffle strips having lower portions extending across the entire lower end portions of the diffuser and constituting means to block light from escaping between the end panels and the diffuser, said baifle strips also having flexible portions fixed at their lower ends with reference to said end panels and comprising free upper ends adjacent the upper portions of said side panels to block light from escaping'between upper portions of the end panels and the diffuser, while also permitting inward displacement of the side panels whereby said flanges are disengageable from said support channels.

3. A luminaire structure attached'to' a room ceiling; a lamp supporting means mounted in the ceiling and having lamp holders therein, a diffuser attached to said luminaire; said diifuser comprising an element of translucent material; said diffuser being substantially W-shaped in cross section and having downwardly and inwardly sloping side panels and an arched re-entrant portion coextensive with the lower edges of said side panels, said re-entrant portion being partially hidden from view from the side of the luminaire, whereby the total luminant surface is increased with corresponding decreased lumens per unit area, while the luminant surface visible from the side of the luminaire is decreased; said side panels being of vertically graduated thickness with the greatest thickness of the panels being toward the upper edges thereof, whereby the light transmitting capacity of the panels is progressively decreased toward the upper edges thereof and brightness contrast between the luminaire and the adjacent portions of the ceiling is avoided, the upper edges of said side panels being positioned closely adjacent said ceiling. a

4. The structure according to claim 3 wherein the lamp supporting means includes spaced inwardly directed flanges and wherein the diffuser is an elongated flexible member whereby the side panels may be deflected inwardly for insertion in and removal from the flanges.

References C itedin the file of this patent UNITED STATES PATENTS 1,763,963 Guth June 17, 1930 1,814,339 Sato July 14, 1931 1,941,079 Exehnans Dec. 26, 1933 2,259,151. Claspy Oct. 14, 1941 2,331,774 Guth Oct. 12, 1943 2,348,930 Schepmoes May 16, 1944 2,640,149 Arenberg May 26, 1953 2,643,328 Elmendorf June 23, 1953 2,659,811, Wakefield Nov. 17, 1953 

